NEW YORK — New York City’s Board of Health approved regulations Tuesday that require any restaurant chain that operates 15 outlets nationwide to display items’ calorie counts on menus, menu boards or food tags. The city’s health commissioner Dr. Thomas R. Frieden, quoted in the New York Times, said he sees the regulations as a powerful weapon in the fight against obesity. As they did when New York City mandated elimination of trans fats from food served in its restaurants, other cities and st